Lifetime extension of French 900 MWe NPPs:
IRSN's role
IRSN FACT SHEETSJanuary 2021

www.irsn.fr

A major challenge concerning more than half of the French nuclear power reactors
RP4-900 and IRSN
Expertise> 40 public opinions> 200,000 hours of work, i.e.
over 130 full-time
equivalents

Built in the 1980s, the 32,900 MWe reactors of the French nuclear fleet are all gradually arriving at the 40-year service life
used as an assumption when they were designed. EDF wished to extend their service life beyond 40 years. Through its
technical expertise applied since 2014 on this subject, as part of the periodic review associated with the fourth ten-year
safety reassessment of these reactors (RP4-900), IRSN supports the Nuclear Safety Authority (ASN) in its decisionmaking. The safety objectives of this review, defined by ASN, are specifically aimed at getting closer to the level of safetyof new generation reactors – in France, the EPR reactor located at Flamanville (north-west of France) – i.e. improving theprevention of fuel meltdown accidents as well as the protection of facilities against external loads and mitigating theconsequences of accidents for people and the environment.

> 250 different experts
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CLIs, and the population
across France
Contributions fromexchanges> Frequently asked
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themes resulting fromquestions from thepopulation> 4 videos> 9 opinions explicitly
answering questions from
CLIs and the Accli> and 2 commented andillustrated opinions

IRSN's safety assessment and its findings
At this stage, IRSN’s assessment shows that the safety objectives should be able to be achieved, subject to significant
additions to the safety demonstration and additional modifications to the facilities, and subject to the specifics of thesites to be inspected at a later date.
In particular, IRSN's analysis highlights:▪ improvement, by the operator, of its organization and its processes relating to control of the facility compliancewith the applicable safety requirements and aging, this improvement must be further consolidated in order todetect and handle deviations quickly and improve the risk assessment of maintenance operations;▪ the desire to get closer to the level of safety targeted for new generation reactors and to integrate feedback fromthe Fukushima-Daichi accident, which led EDF to plan a significant program of modifications to its facilities;▪ the modifications and justifications expected are of larger extent for the reactors of the Bugey power station thanfor the other 900 MWe reactors.

Contact
Emmanuelle Mur
Tel. +33(0)1 58 35 96 71
Registered office31, av. de la Division Leclerc
92260 Fontenay-aux-RosesIRSN also recommended:
IRSN is a French Stateowned industrial andcommercial establishment(EPIC) the missions, status,and operation of which are
determined by Articles L59245 to L592-49 and R592-39
to R592-61 of the French
Environment Code. IRSN isunder the joint supervision ofthe French Minister for theEnvironment, the French the
Minister of Defense, and theFrench Ministers of Energy,
Research, and Health.

▪ additional checks on safety-relevant equipment, and special tests, in addition to those carried out periodically. In thisrespect, the decommissioning of the Fessenheim power plant's two reactors could make it possible to carry out
assessments on equipment difficult to access on reactors in operation;

As a public expert, IRSN
advances scientificknowledge to manage all
nuclear and radiation risks.
Through its research,
methods, and interactions
with all stakeholders, IRSN
assesses these risks andtheir consequences
independently. It thus
contributes to theirprevention, detection, andthe limitation of their
possible effects, in order toprotect the population andthe environment.

▪ the planned reinforcement of the back-up water supply to the steam generators;▪ additional studies relating to the risk of clogging of water recirculation systems required to cool reactors in the eventof an accident as well as modifications intended to reduce this risk;▪ additional modifications necessary to achieve the objectives defined by ASN in 2013 for the continued operation ofreactors beyond 40 years.
Regarding the prevention of core meltdown accidents, IRSN notes:▪ the installation of Emergency Diesel Generators (EDG), as part of the post-Fukushima "hard core", which hassignificantly improved safety;▪ the planned improvement of protection, on each site, against extreme natural events, such as flooding or high winds;▪ the need to improve the supply of boron water to the reactor core to control its reactivity in certain situations similar
to those of the Fukushima-Daiichi accident.
Regarding the mitigation of the consequences of core meltdown accidents, IRSN notes:▪ the means available to cool the corium (melted core) in the containment, following vessel breakage, and the need tocontinue studies with a view to reinforcing certain concrete aprons;▪ the new system allowing heat removal from the containment, without resorting to the venting and filtration systeminstalled (sand filters), and the need to diversify and strengthen the means of adding water to the containment toavoid venting.

Dialog with civil society
Continuous interaction between civil society and IRSN from the start of the assessment, both as part of the consultation
organized by the French high committee for transparency and information on nuclear safety (HCTISN) and as part of thetechnical dialog co-organized with the National Association of Local Information Committees and Commissions (Anccli),
have shown the reciprocal benefit drawn by the nuclear safety expert and the population of such an approach, in particular:
the possibility of dialog between them on complex subjects with high technical content;enrichment, through the perspective of civil society, of IRSN’s safety assessments relating to RP4-900 and the projectto extend reactor service life.
IRSN considers it necessary to continue exchanges between all stakeholders through technical dialog organized inconnection with the Local Information Committees (CLIs) in the regions concerned by these reviews.

The French 900 MWe fleet
At the end of 2020, 56 reactors were in operation, 32 of which had a power of900 MWe. Both reactors in Fessenheim (northeast of France) were shut downin February and June 2020.
Commissioned between 1977 and 1987, the 900 MWe reactors were designed,
for some of their components, on the basis of an assumption of a 40-year
service life.
They are subject to ten-year inspections intended to verify their compliancewith their safety standards and to upgrade them in order to bring their safetylevel up to state-of-the-art standards.
The operating permit for a reactor is issued for an unlimited period of time, but
is reviewed every ten years, in accordance with the 2006 French law ontransparency and security in the nuclear field.
Number of 900 MW reactors

In 2016, ASN defined the major objectives to be achieved in order to manage
the fourth periodic review of 900 MWe reactors.